2.2.3. Island PLES System Construction

The identification of a rural place or village varies in different countries. The term in this paper is identified as a region that is outside the urban built-up area and is a system of the territorial complex with natural, social, and economic functions [37,38].

Based on the island land-use classification formulated by the 908 Special Project (Table 2), the primary industries were emphasized and the ecological and utilized area of the intertidal zones and neritic regions were supplemented. Meanwhile, to allow for the resolution of remote sensing (RS) images, some microscale land-use types that were difficult to acquire from the images were merged and adjusted. The islands' PLES-classificationsystem fit for the studied area was formulated afterward (Table 3).


**Table 2.** Island land-use classification of study area.

The production space (PS) refers to the space dominated by the production functions. The PS includes paddy field, dryland, orchard land, and aquaculture pond, which supports agriculture and marine production. The reservoirs and ponds of the islands in the studied area mainly serve agricultural production and hence are classified as PS.

The living space (LS) refers to the space guaranteeing the survival of humankind and carrying human culture. Many time-honored villages on the islands in the studied area have historical, cultural, scientific, artistic, social, and economic value [39]. Thus, in this classification, the rural residential land was separated from the urban residential land by considering the further assessment and preservation of the traditional villages, and was classified into LS alongside land for the harbor and wharf.

The ecological space (ES) refers to the natural space which can maintain regional ecological security [40]. The mangrove forest is a critical ecological space in the study area, listed in the list of Ramsar Convention wetlands of international importance. Besides, wetlands, sandy beaches, and mudflats in the intertidal zones were highlighted in the PLES classification system. Due to the weak capacity of the islands to withstand natural disasters, this classification also stresses the shelterbelts, which defend against natural disasters, protect production, and maintain ecological balance, so as to highlight the particular ecosystem of the subtropical islands.


**Table 3.** PLES classification and image features (Data resources: *Google Earth*).


**Table 3.** *Cont.*


**Table 3.** *Cont.*
